To reduce the time spent in spraying crops by tractormounted or tractor-drawn equipment and to reduce the number of "tramlines" for the passage of tractor wheels, it is desirable to increase the area of a crop which is sprayed during each traverse of a field. Accordingly, recent years have seen an increase in the width of typical booms for agricultural or horticultural spraying equipment from twelve meters to twenty-four meters or even thirty six meters.
Unfortunately, increasing the length of a boom means increasing its weight, thereby increasing the load on the tractor and increasing the compaction of the land. There is therefore a need for a form of construction which results in a boom which is lighter per unit length than conventional booms whilst still having sufficient strength and rigidity.
Spraying equipment including similar booms may be tractor-drawn or mounted on a tractor, lorry, hovercraft, helicopter or even on a tricycle or bicycle and used for applying de-icing liquid to aircraft runways, similar large areas, or even roads. Spraying booms may also be mounted on ships or structures such as oil rigs, which may be floating or mounted on the sea-bed, and used for spraying chemicals to disperse oil slicks or other pollutants in the sea. In each of these cases there is also a need for a boom which is lighter per unit length than conventional booms whilst still being sufficently strong and rigid.